Dairy Promotes Cancer
In the China study, dairy consumption is directly linked to breast and prostate cancers. The China Study has concluded that casein, the protein found abundantly in cow’s milk, is the most significant carcinogen we are exposed to in our lifetime. The documentary, Forks Over Knives, explores in detail this subject and other health issues involving animal products. This page on dairy causing cancer includes these key facts:
- Dairy increases IGF-1 levels that contributes to cancers.
- Dairy consumption is linked to prostate cancer.
- Dairy consumption is linked to breast cancer.
- Dairy consumption is linked to colorectal cancer.
Cancer
One in two people born after 1960 in a western country will be diagnosed with some sort of cancer during their lifetime. Up to 40 per cent of these cancers could be prevented by lifestyle changes. A poor diet may be responsible for a third of all cancer deaths and is the second largest preventable risk factor for cancer, coming close behind smoking.
Western diets containing meat and dairy, sugar, and highly processed food products, can increase the risk of cancer. On the other hand, whole grain plant-based diets, which include fiber and antioxidants, lower the risk.
The European Prospective Investigation into Cancer and Nutrition (EPIC) study found that vegans had a 19 per cent lower risk of cancer than meat-eaters (fish-eaters had a 12 per cent lower risk and vegetarians 11 per cent lower). The World Cancer Research Fund says that “…most diets that are protective against cancer are mainly made up from foods of plant origin”.
IGF-1 Signaling Trouble
Milk increases levels of the growth hormone IGF-1 in our bodies by stimulating its production in the liver. Increased IGF-1 levels are linked to cancers of the colorectal, breast and prostate. It may also transform pre-existing or benign tumors into a more aggressive form of cancer. Professor T. Colin Campbell, Jacob Gould Schurman Professor Emeritus of Nutritional Biochemistry at Cornell University, says that IGF-1 may turn out to be a predictor of certain cancers in the same way that cholesterol is a predictor of heart disease.
Colorectal Cancer
Colorectal cancer is the third most common cancer in the world. Several lifestyle factors have been linked to it – a Western diet, physical inactivity, obesity, and type 2 diabetes. The links between diet, weight and exercise and colorectal cancer are some of the strongest for any type of cancer and raised IGF-1 levels are implicated. Eating cheese, butter, cream, ice cream and other dairy foods not only increases IGF-1 levels but also increases the risk of becoming overweight and developing diabetes, which increases the risk of colorectal cancer. Dairy foods offer no benefits to good colorectal health while whole grain, plant-based diets containing plenty of fruit and vegetables and low in saturated fat reduce the risk of colorectal cancer.
Breast Cancer
Breast cancer rates in the have risen steeply since the 1970s. The lifetime risk is now one in eight. Only five to 10 per cent of breast cancer cases are caused by genes, most cases are caused by environmental factors. Research from Harvard School of Public Health suggests that nearly a third of all breast cancer deaths in high-income countries are caused by preventable lifestyle factors; alcohol, overweight/obesity, lack of exercise. Women with breast cancer tend to have higher oestrogen levels and a typically meaty and dairy-rich Western-style diet increases the levels of these hormones. In fact, milk and dairy products are the main source of oestrogens in our diet. Changing diet could prevent or limit the progression of the disease as high-fiber, low-fat, vegan diets may lower hormone levels. Soya foods can also reduce breast cancer risk and improve the prognosis for women with the disease. A dairy-free plant-based diet can reduce the risk factors associated with breast cancer and may help those who have been diagnosed with the disease.
Prostate Cancer
Studies indicate collation between high cow dairy consumption and prostate cancer. The lifetime risk of prostate cancer for men is now one in eight. Just five to15 per cent of prostate cancers are linked to genes. So, like breast cancer, most cases are caused by environmental and/or lifestyle factors. Obesity and lack of exercise increases the risk. Rates are higher in countries consuming a typical Western diet. Men who eat lots of saturated animal fats (red meat such as beef, lamb and pork, eggs and butter, whole milk, cheese, and cream) have an increased risk of getting the disease. Diets high in calcium and dairy protein may also increase the risk of prostate cancer. Cow’s milk protein increases IGF-1 levels, a known risk factor for prostate cancer. It has also been suggested that regular exposure to oestrogen in milk from pregnant cows may explain the increased risk of prostate cancer in Western societies.
In the early 2000s, Davaasambuu, a physician and research fellow at the Harvard School of Public Health, began investigating why the rate of prostate cancer in Japan, while much lower than that of the United States, had increased 25-fold over the past 50 years. She and a colleague, the Japanese doctor Akio Sato, examined 36 years of dietary data in Japan and found that the incidence of, and mortality from, prostate cancer correlated most closely with the consumption of milk. Dairy products weren't widely available in Japan until after WWII, when it imported American cows and dairy techniques, and a new law, enacted in 1954, mandated those schoolchildren drink 200 milliliters of milk at every school lunch.
Hormone Levels Link to Cancer Rates
In a follow-up study, Davaasambu found that milk consumption strongly correlated with the rates of breast, ovarian, and uterine cancers in 40 countries. Part of the problem, she believed, was that milk contains high levels of sex hormones such as estrogen. It's well known that estrogens can induce prostate cancer in rats, and some epidemiological studies (but not others) have associated higher blood levels of estrogens in humans with prostate cancer risk. Estrogen imbalances have also been linked to breast cancer, and milk may be a delivery vehicle for the hormone. A 2004 study published in the International Journal of Cancer found that rats fed a diet of milk developed more and larger mammary tumors than those fed a diet of non-dairy milk.
If milk does increase our risk of developing certain cancers, Davaasambuu wondered, then why aren't those cancers more common in traditional cow herding societies? Searching for answers, Sato, her Japanese colleague, took his team to Mongolia, where breast and prostate cancer rates are low. They discovered that whole milk from Japanese Holsteins contains far more estrogen and progesterone (67 percent and 650 percent, respectively) than whole milk from Mongolian cows. If Davaasambuu's theory is correct, the difference in hormone levels could help explain the difference in cancer rates between the two populations.
Davaasambuu and faculty members at the Harvard School of Public Health and Harvard Medical School completed Bostonian and Mongolian milk trials to examine the effects of milk consumption on hormones, growth, and development in prepubertal children. They discovered that Mongolian children drink one-third less dairy than their American counterparts and have lower cancer rates. Newer research suggests that other milk components, including calcium in excess and a hormone called insulin-like growth factor can also cause health problems.